Decrease of organic fluorine compounds in hydrofluoric acid alkylation of hydrocarbons



Much 11. 1947. F. E. FREY 2,417,106

DECREASE OF ORGANIC FLUQRINE COMPOUNDS, IN HYDROFLUORIC ACID, ALKYLATION OF HYDROGARBONS Filed Aug. 26. 1943 SET TLER D IGE STER is I ATT N$ PARAF FIN Patented Mar. 11, 1947 POUNDS IN HYDROFLUORIC ACID AL- KYLATION OF HYDRO CARBONS Frederick E. Frey, Bartlesville, 'olua, assignor to Phillips Petroleum Company, a corporation of Delaware Application August 26, 1943, Serial No. 500,109.

11 Claims. (Cl. 260683.4)

This invention relates to the catalytic production of higher-boiling hydrocarbons from lowerboiling hydrocarbons, and more particularly to the catalytic alkylation of paraffin hydrocarbons in the presence of hydrofluoric acid. 1

In the presence of suitable catalysts, alkylatable hydrocarbons react with unsaturated hydrocarbons or other suitable alkylating reactants to produce higher-boiling hydrocarbons. The reaction, which is known as alkylation, is promoted especially well by hydrofluoric acid. This catalyst yields excellent results with isoparafilns or other branched-chain paraffins and particularly paraf fins with at least one tertiary carbon atom per molecule and with olefins having more than two carbon atoms per molecule. However, under especially favorable circumstances other paraflins and/or olefins may react. Besides paraffins, other alkylatable hydrocarbons, such as aromatic hydrocarbons, can be reacted with an alkylating reactant in the presence of hydrofluoric acid to produce higher-boiling hydrocarbons. Suitable alkylating reactants for the alkylation of either paraflins or aromatics include olefins, relatively polar nonprimary alkyl compounds, such as tertiary and secondary alkyl halides, advantageously fluorides and chlorides, alcohols, and the like. The hydrofluoric acid preferably should be above about 80 per cent in strength and will generally be used with a strength greater than 85,per cent; it is most advantageous when it is substantially anhydrous, or 100 per cent in strength.

The eliluents from hydrocarbon conversion processes catalyzed by hydrofluoric acid contain small but appreciable proportions of organic fluorides. When the effluent comprises mostly butane and/or lighter hydrocarbons, the butane and lighter fractions contain most of the organic fluorides. The presence of these fluorides in the effluent is undesirable because in subsequent operations, as upon being heated, they decompose, liberating hydrogen fluoride, which is corrosive. Although means for removing organic fluorides from hydrocarbons are available, the formation of these fluorides represents an undesirable consumption of hydrocarbons and hydrofluoric acid. A decrease in the extent of formation and/or survival of such fluorides is desirable.

In accordance with one aspect of this invention, the extent of formation and/or survival of organic fluorides in hydrofluoric acid alkylation isdecreased by increasing the time of residence of the alkylation mixture underalkylating condi tions of temperature and pressure. Further improvement is obtained by separating the heavier or acid phase from the lighter or hydrocarbon phase of the emuent, digesting the acid phase so separated, and subsequently recontacting the acid and hydrocarbon phases, before final separation of these phases and isolation of the desired product.

An object of this invention is to decrease the extent of the production and/or survival of organic fluorides in hydrofluoric acid alkylation.

Another object of this invention is to increase the yield of alkylate produced by hydrofluoric acid alkylation.

Another object of this invention is to improve"- inlet 2 controlled by valve 3 and is passed to alkylator 20. This feed is usually chiefly an iso paraffin of four to five carbon atoms per molecule, such as isobutane and/or isopentane, but it generally contains also relatively inertparafllns such as normal butane and propane. Substantially anhydrous hydrofluoric acid is introduced through inlet 4 controlled by valve 5 and is passed to alkylator 20. An alkylating agent, usually one or more olefins, such as, for example, one or more butylenes, enters the system through inlet 6 controlled by valve 1 and is added to the mixture of alkylatable hydrocarbon and hydrofluoric acid at several points through conduits 9, I0, l2 and I4, which are controlled by valves 8, H, II, and I5, respectively.

Alkylator 20 may be any reaction vessel so designed that intimate mixing of the influent mixture takes place, as by stirring devices, perforated plates, bafiles, or the like. In accordance with one feature of this invention, it preferably comprises two zones, olefin-addition zone 2| and after-contacting zone 22. The temperature and the pressure may differ somewhat in thetwo zones, but for present purposes they may be considered substantially uniform throughout both zones. When the alkylation mixture has reached zone 22, olefln addition and the primary reaction of isoparaffin with olefin are substantially complete, but appreciable olefin in combination with the catalyst as alkyl fluorides is still present. By means of zone 22 the time of residence of the mixture under alkylating conditions is increased, whereby at least some of the surviving organic fluorides react with the excess isoparafiin in the mixture. The effective time of residence of the alkylation mixture in the reactor may be further increased by recirculation of part of the mixture by pump 23 through conduit 26 controlled by valve 25. The total residence time of the reaction mixture in alkylator 20 is usually from 1 to 15 minutes, preferably 5 to minutes; times longer than about 10 or minutes require an expenditure of power, to maintain the mixture inemulsified form, that is comparatively excessive, in view of the relatively small additional reaction that occurs. However, this potential additional reaction, which is relatively slow, is important. and the present invention provides specifically for its occurrence, as will be indicated hereinafter. A generally suitable alkylation temperature in alkylator is from '75 to 125 F., although higher or lower temperatures may be employed if desired; usually a temperature from 90 to 110 F. is preferred. The pressure should be suificient to maintain the reactants in the liquid phase, but extremely high pressure is unnecessary. A generally satisfactory volume ratio of acid to hydrocarbon is approximately 1:1, although higher or lower ratios may be used if desired. The over-all mol ratio of alkylatable hydrocarbon to alkylating agent in the feed or feeds is usually between 4:1 and 10:1; local mol ratios within the reactor itself are preferably much higher, such as 100:1 or more.

Conventionally, the effluent from alkylator 20 may be passed via conduits i2 3 and I and through conduit 28 controlled by valve 29 to separator 60; preferably, however, in accordance with one aspect of this invention, the mixture is passed from conduit l 2 5 through conduit 26 controlled by valve 21 to preliminary separator 30, in which the heavier or acid phase is separated from the lighter or hydrocarbon phase by settling and/or cehtrifugation. Although part of the hydrofluoric acid phase may be recycled-to alkylator20 through conduit 3| controlled by valve 32, preferably most or all of the acid phase is passed through conduit 33 controlled by valve 34 to digester 60, wherein the isoparafilin and the alkyl fluorides dissolved in the acid phase are allowed additionaltime in which to react. Digester an is preferably free from agitation means, to conserve power. The temperature and the pressure in digester 60 are usually, although not necessarily, approximately the same as those in alkylator 20. The time of residence of the acid phase in digester $0 is from 15 to 60 minutes, usually preferably to 40 minutes; the optimum time in any specific case may be experimentally determined by one skilled in the art.

The acid phase is passed from digester i0 through conduit ii controlled by valve 42 to contactor 50 for recontacting with the hydrocarbon phase, which is passed from separator 30 to contactor 50 through conduit controlled by valve 36. In contactor 50 the acid and hydrocarbon phases are intimately mixed by any convenient means, whereby an dissolved organic fluorides are extracted by the acid from the hydrocarbon phase and the alkylate formed in digester is extracted by the hydrocarbon phase. This operation is preferably aided by a cooling step, not

shown, to decrease the temperature somewhat below that present in the alkylation and digesting steps. A generally satisfactory temperature for this operation'is 50 to 100 F., although lower or higher temperatures may be used if desired; a preferred temperature is 70 to 90 F. A satisfactory time of residence in contactor 50 is approximately 0.5 to 5 minutes, although it may be more or less if desired; usually approximately 1 to 2 minutes is preferred. From contactor 50 the mixture is passed through conduit 5! controlled by valve 52 to separator 60, in which the acid and hydrocarbon phases are separated by gravity and/or centrifugation, aided if desired by cooling. The acid phase is recycled through conduit 6| controlled by valve 62 to alkylator 20; if desired, any part of the acid may be withdrawn, as through outlet 63 controlled by valve 64, for purification by means not shown before being recycled to alkylator 20. The hydrocarbon phase is passed through conduit 65 controlled by valve 66 to fractionating means l0, which usually is a system of two or more fractionating columns and auxiliary equipment. In this means the hydrocarbon phase is separated into a number of fractions, such as the following: (1)a minor fraction, comprising mainly an azeotropic mixture of hydrofluoric acid and propane, which is withdrawn through outlet 'll controlled by valve 12; (2) a major fraction, comprising mainly isobutane and some hydrofluoric acid, which is recycled through conduit l3 controlled by valve 14 to alkylator 20; (3) a fraction, comprising chiefly normal butane, which is withdrawn through outlet 11 controlled by valve 18; (4) a fraction, comprising chiefly alkylate hydrocarbons that boil in the motor-fuel range, which is withdrawn through outlet 19 controlled by valve and (5) a minor fraction, comprising hydrocarbons boiling above themotorfuel range, which is withdrawn through-outlet 8! controlled by valve 82.

In another arrangement, which is.advantageous because of its simple equipment, the eflluent from alkylator 20, instead of being passed through conduit 26 and valve 27 to separator 30, is passed through conduit 88 controlled by valve 89 to settler-digester 90 which is a vessel of such relatively large dimensions, in comparison with conduit 88 and the coil of alkylator 20, that viscous or streamline, instead of turbulent, flow is maintained, and the reaction mixture becomes separated into two liquid phases. These two phases flow through settler-digester 90 in the direction indicated by the arrows. The isoparafiin and the organic fluorine compounds dissolved in the acid phase react to produce additional alkylate. Since hydrocarbon reactions catalyzed by liquid hydroiiuoric acid do not-proceed at practical velocities unless the reaction mixture is emulsified or unless the two phases are otherwise intimately contacted, the acid phase is thus digested in settlerdigester 90 without initiating undesirable reactions involving the hydrocarbon phase.

Generally the time of residence of the acid phase in settler-digester 90 is 15 to 60 minutes, preferably 30 to 40 minutes; the time of residence of the hydrocarbon phase is usually much shorter, preferably only 1 to 5 minutes. so that the fraction of settler-digester 90 occupied by the hydrocarbon phase is relatively small. The temperature and the pressure in the Settler-digester 90 are preferably, although not necessarily, the same as in alkylator 2'0.

The heavier or acid phase and the lighter or hydrocarbon phase are passed through conduits 9i and B2 in proportions controlled by valves 93 if desired. From recontactor 96 the reaction fluorine content of the hydrocarbon emuent is accomplished as follows: The total efliuent from the alkylation zone is passed to a gravity settler, in which the acid and hydrocarbon phases are separated. .The acid phase is digested for approximately 35 minutes at the temperature of the alkylation zone, 100 F., and is passed to a secon-d contactor, which is maintained at about 80 mixture is sent to settling means, such as separator 60, and it is thereafter treated as previously outlined.

It should be understood that the flow-diagram is schematic; necessary equipment not shown, such as valves, pumps, and heat-exchange equipment, may be supplied by anyone skilled in the art.

Understanding of some aspects of this invention may be facilitated by the following examples:

Example I The effluent from the hydrofluoric acid alkylation of isobutane with butene-2 at 100 to 120" F. and at an average contact time of 8 minutes is passed to -a settler; in which it is separated into a hydrofluoric acid phase and a hydrocarbon phase. The "acid phase is passed to a digester, in which it is digestedfor approximately 25 minutes at the alkylation temperature. The acid phase and the hydrocarbon phase are then passed through a cooling-coil to a. second contactor, in which they are recontacted for a period of 2 minutes at 80 to 100 F. The effluent from the second contactor is passed to a settler, in which it is again separated into acid and hydrocarbon phases. The organic fluorine content of the hydrocarbon phase before recontacting with the acid phase is approximately 0.020 weight per cent; the organic fluorine content of the hydrocarbon phase after recontacting is only approximately 0.003 weight per cent. Thus approximately 85 per cent of the organic fluorine is removed by the hydrofluoric acid phase and is returned by it to the alkylation zone, so that the overall production of alkylate is correspondingly increased. In this operation, the total efiective reaction time is approximately 35 minutes, whereas power for agitation is consumed for only 10 minutes.

Example II In a certain continuous hydrofluoric acid alkylation system for the alkylation of isobutane with olefins of three to four carbon atoms per molecule, the hydrocarbon effluent from the mechanical agitators in which the alkylation mainly occurs averages approximately 0.040 weight per cent, organic fluorine. The average time of residence of the reaction mixture in the alkylation zone comprised by the agitators is 7 minutes. It is known that, by increasing the time of residence for this alkylation system to 40 minutes, the organic fiuorine content of the hydrocarbon efiiuent can be reduced to approximately 0.006 weight per cent. Although this reduction in organic fluorine content would result in a saving of almost 400 pounds of hydrofluoric acid per day for the alkylation system concerned, the increase in power requirement makes the advisability of such an increased time of residence doubtful. However, in accordance with the present invention, a comparable reduction in the organic ment is only a fifth of that in the F., and in which the acid and hydrocarbon phases are recontacted for approximately 1 minute. The eflluent from the second contactor is passed to a settler for final phase-separation. Although in this procedure the decrease in organic fluorine contentof the hydrocarbon eflluent is approximately equivalent to that eilected by a total agitation time of minutes, the power requireprocedure using continuous agitation.

Because the invention may be practiced in many ways other than those specifically shown herein, and because many modifications will be apparent to anyone skilled in the art, the invention should be limited only as specified in the appended claims.

I claim:

1. In a process for alkylating an alkylatable hydrocarbon with an olefin under alkylation conditions to produce higher-boiling hydrocarbons in which the reactants are intimately mixed with hydrofluoric acid to form an alkylation mixture, decreasingthe content of organic fluorides in the hydrocarbon eflluents by the improvement which comprises separating said alkylation mixture when said alkylation is substantially complete into a liquid hydrocarbon phase and a liquid acid phase, maintaining said acid phase separate from said hydrocarbon phase and at a reaction temperature for a period sufficient for organic fluorine compounds dissolved in said acid phase to be substantially completely consumed by alkylation of alkylatable hydrocarbons likewise dissolved in said acid phase, intimately remixing the two liquid phases and maintaining said mixture for a period of time suificient to decrease the amount of organic fluorine compounds in said hydrocarbon phase.

2. The improvement of claim 1, in which said period for treating said separated acid phase is 15 to 60 minutes.

3. The improvement of claim 1, in which said period for treating said separated acid phase is 30 to 40 minutes.

4. In a process in which an alkylatable hydrocarbon, an olefin, and hydrofluoric acid are intimately mixed together to form an alkylation mixture at to F., the improvement which comprises limiting the mixing of said alkylation mixture to a period of 1 to 15 minutes, separating said alkylation mixture into a liquid acid phase and a liquid hydrocarbon phase, maintaining said acid phase separate from said hydrocarbon phase and at a reaction temperature between 70 and 90 F. for a period of 15 to 60 minutes, and remixing said acid phase and said hydrocarbon phase for a to 5 minutes.

5. A process for the production of a normally liquid paraflinic hydrocarbon material which comprises reacting a low-boiling isoparamn with an olefin in the presence of substantially anhydrous hydrofluoric acid, recycling at least a part of the reaction mixture to the alkylation zone, subsequently maintaining said mixture at alkylating conditions for an additional period of time, separating the reaction mixture into a liqperiod of approximately 0.5

uid hydrocarbon phase and a liquid acid phase, digesting the acid phase under alkylating conditions, recontacting the acid phase and hydrocarbon phase under alkylating conditions, separating again the resulting mixture into a hydrocarbon phase and an acid phase, recycling the acid phase to the alkylating zone, and fractionating the hydrocarbon phase to obtain a normally liquid paraflinic material boiling in the motorfuel range.

6. The process of claim in which the lowboiling isoparaflm is isobutane.

7. The processof claim 5 in which the olefin is a butylene. I

8. A process for decreasing the amount of organic fluorine compounds present in the liquid hydrocarbon phase which is recovered from at fiuents of a process for alkylating a low-boiling isoparaflln hydrocarbon with an olefin in the presence of a liquid hydrofluoric acid alkylation catalyst to produce higher-boiling parafinic hydrocarbons when eiiiuents oil such an alkylation are passed to a separating zone wherein a separation is efiected between a liquid hydrocarbon phase and a liquid hydrofluoric acid phase, which comprises maintaining said liquid hydrofluoric acid phase at'a temperature between 75 and 125. F. for a reaction period of at least 15 minutes while substantially free from intimate admixture with a separate hydrocarbon phase, subsequently intimately readmiring said liquidhy drofluoric acid phase and said liquid hydrocarbon phase for a period of time not to exceed about 5 minutes, and separating a resulting hydrocarbon phase. I

9. A process for decreasing the amount of organic fluorine compounds present in the liquid hydrocarbon phase which is recovered from ei-= fluents of a process ior aljkylating a low boiling alkylatable hydrocarbon with an clhylating reactant in the presence or a liquid hydrofluoric acid alkylation catalyst to produce higher-boil ing hydrocarbons when efiuents oi such an alkylation are passed to a separating zone wherein a separation is effected between a liquid hydrocarbon phase and a liquid hydrofluoric acid phase, which comprises maintaining said liquid hydrofluoric acid phase at a temperature between 75 and 125 F. for a reaction period of at least 15 minutes while substantially free from intimate admixture with a separate hydrocarbon phase, subsequently intimately admixing said liquid hydrofluoric acid phase and the aforesaid liquid hydrocarbon phase for a period oi time not to exceed about 5 minutes, and separating a resultant hydrocarbon phase.

10. An improved process for reacting on alkylatable hydrocarbon'with an alkylating reactant in the presence of a hydrofluoric acid allrylatidn' catalyst to produce a hydrocarbon mixture containing no more than a minor amount of organic fluorine compounds, which comprises subjecting a mixture comprising an alkylatable hydrocarbon and an alkylating reactant to alkylation reaction conditions in the presence of a bysaid zone is 15 to 60 minutes and of said hydrocarbon phase is l to 5 minutes, subsequently in-= timately admixing" said withdrawn liquid phases' and maintaining said intimate admixing for a period not exceeding 5 minutes and sumcient to decrease the amount of organic fluorine compounds in said hydrocarbon phase, subsequently separating a resulting hydrocarbon phase and recovering therefrom an alkylate traction as a product of the process.

11. An improved process for reacting a lowboiling isoparaflin with an alkylating reactant in the presence oi. a hydrofluoric acid alkylation catalyst to produce higher-boiling paramn hydrocarbons, which comprises'reactlng such an isoparaflin and an allrylating reactant under alkyla tion conditions in the presence of a liquid hydrofluoric acid alkylation catalyst, separating from efiuents of said reaction a liquid hydrocarbon phase and a liquid hydroflouric acid phase, maintaining said separated liquid hydrofluoric acid phase at a temperature between about and about F. for a period of about 15 to 60 minutes while free from admixture with a separate hydrocarbon phase, during which time chemical reactions continue within said hydrofluoric acid phase, subsequently intimately admixing said liquid hydrofluoric acid phase and aforesaid liquid hydrocarbon phase for a period of time not to exceed about five minutes, during which time a decrease in the organic fluorides in said'hydrocarbon phase takes place, separating said last intimate admixture into a liquid hydrocarbon phase and a liquid hydrofluoric acid phase, and

recovering from said last hydrocarbon phase higher-boiling paramn hydrocarbons produced in said almlation.

' FREDERICK E. FREY.

nm aaeueus orrso The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,223,938 Pevere Dec. 3, 1940 2,258,236 Benedict Oct. 7, 1941 2,267,097 Hatch Dec. 23, 1941 2,271,860 Goldsby Feb. 3, 1942 2,307,773 Eglofi Jan. 12, 1943 2,307,799 Linn Jan. 12, 1943 2,320,629 Matuszak June 1, 1943 2,335,704 Smith Nov. 30, 1943 2,354,641 Gerhold July 25, 1944 2,322,800 Frey June 29, 1943 2,372,338 Penisten Mar. 27, 1945 

